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This study investigated the sensitivity of the positive matrix factorization (PMF) model using concentrations of PM2.5-bound elements in Windsor, Ontario, Canada. Five scenarios were devised to assess impacts of input data on source identification, source contributions, and model performance. The study found that the model outcomes and performance were not sensitive to data below method detection limits (MDLs) being replaced with ½ MDLs, nor whether brown carbons (BrCs) data were excluded. By analyzing two episodic events individually, unique factors of fireworks and mineral dust were identified for each of the two episodes. Moreover, PMF model performance was improved greatly for event markers of the episodes and elements with less variability in concentration when compared with the base case scenario. Excluding the two episodes from the entire dataset had little impact on factor identification and source contributions but improved the model performance for three out of twelve elements unique to the two episodes. Overall, the PMF model outcomes and performance were sensitive to percentages of concentrations below MDLs and element concentrations with large variability due to high concentrations observed in episodes. Our findings are useful for dealing with data below MDLs and episodic events in conducting future PMF source apportionment of PM2.5-bound elements. [ABSTRACT FROM AUTHOR]

While transportation emissions have declined over the past several decades, volatile organic compound (VOC) emissions from solvent use applications have increased as urban areas expand. In this work, the Canadian air quality model (GEM-MACH-TEB) is used to assess the importance of solvent emissions during the Michigan Ontario Ozone Source Experiment (MOOSE). Model predictions are compared to ozone and total mono-substituted aromatics (TOLU) observations collected in Windsor, Ontario. For summer 2018, model estimates of TOLU from solvent emissions are smaller (30% for an 8 h daytime average) in Windsor than estimates from positive matrix factorization (44% for a 24 h average). The use of updated U.S. solvent emissions from the EPA's VCPy (Volatile Chemical Product framework) for summer 2021 simulations increases the solvent use source contribution over Detroit/Windsor (30–50% for an 8 h daytime average). This also provides a more uniform spatial distribution across the U.S./Canada border (30–50% for an 8 h daytime average). Long-chain alkanes are the dominant speciation in the model's air pollutant emission inventory and in the observation-derived solvent use factor. Summertime 8 h daytime ozone decreased by 0.4% over Windsor for a 10% solvent use VOC emission reduction scenario. A 10% mobile NOx emission reduction scenario resulted in a 0.6% O3 decrease over Windsor and more widespread changes over the study region. [ABSTRACT FROM AUTHOR]

Ambient fine particulate matter (PM2.5) levels in Windsor, Ontario, Canada, are impacted by local emissions and regional/transboundary transport input and also attributable to secondary formation. PM2.5-bound elements were monitored hourly in Windsor from April to October 2021. Observed concentrations of the elements were generally comparable to historical measurements at urban sites in Ontario. A clear diurnal pattern was observed for most of the elements, i.e., high in the morning and low in the afternoon, mostly related to evolution of atmospheric mixing heights and local anthropogenic activities. Conversely, sulfur showed elevated levels in the afternoon, suggesting conversion of gaseous sulfur dioxide to particulate sulphate was enhanced by increased ambient temperatures. Five source factors were resolved using the US EPA positive matrix factorization model, including three traffic-related sources (i.e., vehicular exhaust, crustal dust, and vehicle tire and brake wear factors) and two industrial sources (i.e., coal/heavy oil burning and metal processing factors). Overall, the three traffic-related sources were mostly local and contributed to 47% of the total elemental concentrations, while the two industrial sources may originate from regional/transboundary sources and contributed to 53%. Measures to control both local traffic emissions and regional/transboundary industrial sources would help reduce levels of PM2.5-bound elements in Windsor. [ABSTRACT FROM AUTHOR]

There have been several methods employed to quantify individual-level exposure to ambient traffic-related air pollutants (TRAP). These include an individual's residential proximity to roads, measurement of individual pollutants as surrogates or markers, as well as dispersion and land use regression (LUR) models. Hopanes are organic compounds still commonly found on ambient particulate matter and are specific markers of combustion engine primary emissions, but they have not been previously used in personal exposure studies. In this paper, children's personal exposures to TRAP were evaluated using hopanes determined from weekly integrated filters collected as part of a personal exposure study in Windsor, Canada. These hopane measurements were used to evaluate how well other commonly used proxies of exposure to TRAP performed. Several of the LUR exposure estimates for a range of air pollutants were associated with the children's summer personal hopane exposures (r = 0.41–0.74). However, all personal hopane exposures in summer were more strongly associated with the length of major roadways within 500 m of their homes. In contrast, metrics of major roadways and LUR estimates were poorly correlated with any winter personal hopanes. Our findings suggest that available TRAP exposure indicators have the potential for exposure misclassification in winter vs. summer and more so for LUR than for metrics of major road density. As such, limitations are evident when using traditional proxy methods for assigning traffic exposures and these may be especially important when attempting to assign exposures for children's key growth and developmental windows. If long-term chronic exposures are being estimated, our data suggest that measures of major road lengths in proximity to homes are a more-specific approach for assigning personal TRAP exposures. [ABSTRACT FROM AUTHOR]

This study investigates temporal variations and long-term (1996–2015) trends of ground-level O3 (ozone) and its precursors, NOx (nitrogen oxides), and volatile organic compounds in Windsor, Ontario, Canada. During the 20-year study period, NOx , non-methane hydrocarbon concentrations, and ozone formation potential decreased significantly by 58 %, 61 %, and 73 %, respectively, while O3 concentrations increased by 33 % (20.3 ppb in 1996 vs. 27 ppb in 2015). Our analysis revealed that the increased annual O3 concentrations in Windsor were due to (1) decreased O3 titration (by 50 % between 1996 and 2015) owing to declining nitric oxide concentrations, which is suggested by a slightly decreasing trend of annual mean total O3 concentrations after the titration effect is removed, (2) reduced local photochemical production of O3 because of dwindling precursor emissions, and (3) an increased background O3 level that has a greater impact on the low-to-median concentrations. The net effect of those factors is decreasing peak O3 levels during the smog season from May to September but an overall increasing trend of annual means. These results indicate that the emission control measures are effective in reducing peak ozone concentrations. However, challenges in lowering annual O3 levels call for long-term collaborative efforts in the region and around the globe. [ABSTRACT FROM AUTHOR]

This study investigated temporal variability of ground-level ozone (O 3) during smog season in Windsor, Canada and surrounding states of the US during 1996–2015. Cluster analysis classified six sites into two groups with similar features of O 3 concentrations. The first group consists of four urban/suburban sites, Windsor, Allen Park and Lansing in Michigan, and Erie in Ohio, and the second group includes two rural sites, Delaware and National Trail School in Ohio. The similarities among all six sites include (1) diurnal and seasonal variability of O 3 concentrations owing to similar weather conditions, and (2) decreasing peak O 3 (95th percentile) concentrations due to reduced emissions of precursors, thus less photochemical O 3 formation. However, how O 3 levels changed with reduced NO X emissions during the study period and on weekends differed between the two groups. Lower O 3 concentrations were recorded at urban/suburban sites (30 ppb) than at rural sites (34 ppb). At urban sites, annual smog season O 3 concentrations increased by 0.12–3.2 ppb/year. The increasing trends occurred at all percentile levels except for 95th percentile and in most months, due to weakened NO titration effect. At the rural sites, smog-season O 3 concentrations decreased by 0.01–2.71 ppb/year. The decreasing trends were observed at 50-95th percentile levels and in most months. Between the two groups, the urban/suburban group had a greater increment in weekend O 3 concentrations (3.3 vs. 1.6 ppb) due to a greater reduction of local NO emissions on weekend, thus, weakened NO titration effect. Overall, O 3 formation was more sensitive to VOCs during the study period; however, the O 3 formation regime gradually shifted toward more sensitive to NO X during 1996–2007 then became more sensitive to VOCs during 2008–2015. Therefore, controlling anthropogenic VOC emissions is needed to effectively mitigate O 3 pollution in the study region. [Display omitted] • Lower O 3 concentrations observed at urban/suburban sites than at rural sites. • Peak O 3 decreased at all sites suggesting effective O 3 precursor emission control. • O 3 increased at low-to-mid percentile levels due to weakened NO titration effect. • O 3 formation was more sensitive to VOC in the study area but with variations. • Controlling anthropogenic VOC emission is needed to effectively mitigate O 3. [ABSTRACT FROM AUTHOR]

This study analyzes the crashes that occur at midblock called “midblock crashes” in an urban arterial road. The association of midblock crashes with various factors was examined using the 7-year (2000–2006) crash data on a section of a divided arterial road in Windsor, Ontario, Canada. To account for difference in traffic volume and road geometric factors between two directions of travel in a divided road, the data were collected for two directions separately. The results of log-linear models using these bidirectional data show that midblock crashes are more likely to occur on the road sections with access points and high percentage of trucks (>20%). The results of logistic regression models show that median opening, driver age/gender, lighting, time of day, and day of week are associated with different types of crashes classified by the vehicles involved in crashes. The study shows the importance of analyzing midblock crashes using the bidirectional data by vehicle type in urban divided arterial roads with high truck volume. [ABSTRACT FROM AUTHOR]

Abstract: Windsor (Ontario) is located on the Canada-US border. Some believe that the heavy industrial facilities such as power generation and automobile production in the neighbouring regions of US greatly affect Windsor''s air quality. This study investigates the frequency of air mass exchange between Windsor and the neighbouring US states. Two-day (48-hr) and one-day (24-hr) back trajectories were run using the Hybrid Single-Particle Langrangian Integrated Trajectory (HYSPLIT) model. Windsor Airport (42.27o N, 82.96o W) was the starting point. The model resolution was three days a week. Two calendar years, 2008 and 2009, were modeled thus seasonal and inter-annual variations could be observed. It was found that the fraction of air mass parallel to the border is small. When considering the 48-hr trajectories on an annual basis, 53-55% of air masses arriving Windsor were from the US, whereas the 24-hr trajectories showed a much higher percentage (81-82%). The inter-annual variability between 2008 and 2009 was small. In both years, winter had higher frequency of US to Canada transport than Canada to US. In the other three seasons (spring, summer and fall), one year had more frequent US to Canada transport while the other year had less. It was concluded that overall the US-Canada transport had a higher frequency. However, this alone is inadequate to support the claim of air masses coming from US greatly affect Windsor air quality. Further analyses using state and province wide emission densities and ambient concentrations were conducted for a two-week period during each year to quantitatively assess the trans-boundary movement of air pollutants. Statistical analyses showed no consistent, significant correlations between the travel path of the air mass prior to arrival and the measured NO2 or PM2.5 concentrations at the receptor. [Copyright &y& Elsevier]

Air Quality Health Index (AQHI) is a scale designed in Canada to help residences understand the impact of air quality on health. This study investigated temporal variability of daily AQHI and impact of regional transport on AQHI in Windsor, Ontario, Canada from 2016 to 2019. The four-year average daily AQHI was 2.9, slightly below the upper limit of the low health risk level of 3. AQHI value decreased from 2.95 to 2.81 during the study period, indicating the improvement of air quality. Half of the days, AQHI were 3 regardless of season. AQHI was higher in the warm season (3.1) than in the cold season (2.6) due to more frequent moderate risk days (27%, AQHI = 4) in warm season and more frequent low risk days (42%, AQHI = 2) in the cold season. Among the three pollutants considered, O3 was the most frequently reported dominant contributor to daily AQHI (88% of days), followed by NO2 (12%), especially in the cold season, with small contribution from PM2.5 (<1%). Trajectory analysis found that AQHI ≤ 3 days were closely associated with air masses from the north and northwest, whereas AQHI > 3 days were closely associated with air masses from the west and southwest. This is because northerly flows brought in clear air mass owing to less industrial facilities. Polluted air masses were transported from the south of Windsor, where several industrial states of the US were located. Directional AQHI resembles O3 more than NO2 or PM2.5 concentrations do. Further improvement of AQHI in Windsor could be challenging because O3 concentrations have continued to increase in recent years. Thus, more effective control measures to mitigate O3 pollution are warranted to reduce its impact on human health and the environment. [ABSTRACT FROM AUTHOR]

This study is aimed at identifying the determinants of intra‐urban variation in ambient concentrations of nitrogen dioxide (NO 2 ) in Windsor, Ontario, Canada, and to develop a model to predict NO 2 in the city. NO 2 samples were collected over a two‐week period during winter 2004 by using passive samplers in 50 locations across Windsor. A land use regression (LUR) model was constructed to generate independent variables that could best predict NO 2 concentrations across the city. We tested 71 variables of land use, traffic, road characteristics, population and dwelling counts, and physical geographic variables such as elevation. The final model contained five variables: distance to the Ambassador Bridge, daily traffic on Class 1 and Class 2 arterial roads within 400 m, industry within 600 m, and total population within 700 m. All the variables were statistically significant and had the expected direction of correlation. The final regression model yielded a coefficient of determination, R 2 , of 0.88. The spatial variations captured in this analysis are being used to guide the selection of participants for a number of Health Canada studies. [ABSTRACT FROM AUTHOR]

This study investigated impacts of regional transport and meteorology on ground-level ozone (O3) in the smog season (April–September) during 1996–2015 in Windsor, Ontario, Canada. Data from five upwind stations in the US, which are within 310 km (i.e., Allen Park and Lansing in Michigan, Erie, National Trail School, and Delaware in Ohio), were included to assess the regional characteristics of O3. The five US stations showed high degrees of similarity with O3 concentrations in Windsor, with overall strong correlations (r = 0.567–0.876 for hourly O3 and r = 0.587–0.92 for 8 h max O3 concentrations) and a low degree of divergence, indicating that O3 pollution in the study area shares regional characteristics. Meteorological conditions played important roles in O3 levels in Windsor. High O3 concentrations were associated with southerly and southwesterly air mass from which polluted and hot air mass was transported and that enhanced local photochemical O3 production. In contrast, northerly flows brought in clean, cool, and dry air mass, and led to low O3 concentrations. Strong correlations were found between numbers of days with 8 h max O3 concentrations greater than 70 ppb and numbers of days with daily max temperature greater than 30 °C, as well as between daily max temperatures and 8 h max O3 concentrations. Nearly half (45%) of the high O3 days (≥90th percentile) occurred in dry tropical weather during 1996–2015, and the 90th percentile 8 h max O3 was associated with dry tropical weather. Occurrences of both southerly flow hours and dry tropical weather type in the smog season increased during the study period. If there were more hot and dry days in the next few decades due to climate change, the effect of emission control on reducing peak O3 values would be diminished. Therefore, continued regional and international efforts are essential to control precursors' emissions and to mitigate O3 pollution in Windsor. [ABSTRACT FROM AUTHOR]

Background We examined the impact of data source and exposure measurement error for ambient NO 2 on risk estimates derived from a case-crossover study of emergency room visits for asthma in Windsor, Canada between 2002 and 2009. Methods Paired personal and fixed-site NO 2 data were available from an independent population (47 children and 48 adults) in Windsor between 2005 and 2006. We used linear regression to estimate the relationship and measurement error variance induced between fixed site and personal measurements of NO 2 , and through a series of simulations, evaluated the potential for a Bayesian model to adjust for this change in scale and measurement error. Finally, we re-analyzed data from the previous case-crossover study adjusting for the estimated change in slope and measurement error. Results Correlations between paired NO 2 measurements were weak ( R 2 ≤0.08) and slopes were far from unity (0.0029≤ β ≤0.30). Adjusting the previous case-crossover analysis suggested a much stronger association between personal NO 2 (per 1 ppb) (Odds Ratio (OR)=1.276, 95% Credible Interval (CrI): 1.034, 1.569) and emergency room visits for asthma among children relative to the fixed-site estimate (OR=1.024, 95% CrI 1.004–1.045). Conclusions Our findings suggest that risk estimates based on fixed-site NO 2 concentrations may differ substantially from estimates based on personal exposures if the change in scale and/or measurement error is large. In practice, one must always keep the scale being used in mind when interpreting risk estimates and not assume that coefficients for ambient concentrations reflect risks at the personal level. [ABSTRACT FROM AUTHOR]

As part of a multi-year personal exposure monitoring campaign, we collected personal, indoor, and outdoor levels of 188 volatile organic compounds (VOCs). In 2005, data were obtained for 48 non-smoking adults from Windsor, Ontario in order to assess their exposure to VOCs based on their daily routines and characteristics of their homes. During the 8-week winter and summer sampling sessions, five repeated 24-h measurements were obtained for each home. This paper focuses on the analysis of 18 VOCs: 11 have been declared toxic as defined under the Canadian Environmental Protection Act, [1999. Statutes of Canada. Act assented to September 14, 1999. Ottawa: Queen''s Printer. Available at Canada Gazette (Part III) 22(3): (Chapter 33). http://canadagazette.gc.ca/partIII/1999/g3-02203.pdf], and seven are commonly found in household and personal care products. Results of mixed effects models indicate that personal exposure to these VOCs can be largely predicted by indoor concentrations, with models including indoor concentrations found to have an r 2 value for the fixed effects ranging from 58.4% to 87.2% for the CEPA toxic VOCs and from 41.7% to 90.1% for the commonly found VOCs. Given that people spend the majority of their time inside their home, characteristics of the home such as air exchange rates, type of garage, and type of stove have a greater potential to impact personal exposures. [Copyright &y& Elsevier]